The present invention is generally directed to a non-impact printing apparatus and in particular to a printing apparatus and method of forming characters or images on a transfer medium by transferring a thermoplastic magnetic ink from an ink medium to a transfer medium by application of heat and magnetic force to the ink.
Several compact and low cost non-impact printing methods utilizing magnetic ink have been proposed. Japanese Patent Application No. 52-96541 is directed to a printing apparatus in which magnetic inks are used for magneto-thermal transfer of the melted ink. A magnetic attraction forced produced by a magnet that is separate from the heat source acts on the ink to form desired thermal images. FIG. 1 discloses such a printer 50. The printer is arranged with a thermal head 51 proximate an ink medium 52 including a base film 53 and thermoplastic magnetic ink 54. A transfer medium 55 for selectively receiving the ink is placed proximate to ink medium 52 and a magnet 56. Thermal head 51 and magnet 56 are on opposite sides of transfer medium 55.
When thermal energy is applied to base film 53 by thermal head 51 the thermoplastic magnetic ink 54 is liquified so that the melted ink medium can be pulled off of base film 53 and onto transfer paper 55. Various ways are known for increasing the rate at which the ink which is to be deposited on the paper, is melted and for increasing the rate at which the melted ink is transferred to the paper. These approaches are used so that high quality characters and images can be printed on any type of transfer paper including those having great surface roughness.
However, the known printers include the transfer medium sandwiched between the thermal head and the magnet. In addition, they have separate thermal application and magnetic attraction force mechanisms. This known structure causes two distinct problems with the prior art printing approaches. First, the thickness of the transfer medium is severely restricted to a narrow range of hickness. The thicker the transfer medium is the further the magnetic head, which generates the magnetic attraction force, is spaced apart from the magnetic ink. As a result, the magnitude of the magnetic attraction force is reduced, which reduces the efficiency of transferring the magnetic ink. Second, when the printer in accordance with the prior art approach is adapted for use as a serial printer the magnetic and thermal heads must be maintained with accurate spacing relative to each other and to the ink medium and transfer medium. Thus, the magnetic head and the thermal head must move in a synchronized manner. Complicated constructions are thus required to insure that the magnetic and thermal heads are accurately positioned and the cost of such a printer significantly increases. The hard cost, or cost of components used in such a printer is thus increased.
Accordingly, there is a need for an improved non-impact printer and printing method utilizing thermoplastic magnetic ink on a base film which prints high quality characters and images on transfer papers of varying degrees of roughness and thickness while simplifying the mechanical structure and reducing the cost of the printer.